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IIT-JEE 2011 EXAMINATION PAPER - 1 (HELD ON : 10 - 04 - 2011) PART - I (CHEMISTRY) SECTION - I (TOTAL MARKS : 21) (Single Correct Answer Type) This section contains 7 multiple choice questions. Each question has four choices (A), (B), (C) and (D), out of which ONLY ONE is correct. 1. Geometrical shapes of the complexes formed by the reaction of Ni2+ with Cl–, CN– and H2O respectively, are - (A) octahedral, tetrahedral and square planar (B) tetrahedral, square planar and octahedral (C) square planar, tetrahedral and octahedral (D) octahedral, square planar and octahedral 1. Ans.(B) EN [NiCl 4 ]2- , [Ni(CN)4 ]2- , [Ni(H 2O) 6 ]2+ Cl Cl Ni 2– NC CN 2– H2 O H2 O OH2 Ni OH2 OH2 2+ Cl Ni LL Cl NC CN OH2 sp3 dsp 2 sp3d2 tetrahedral square planar octahedral 2. AgNO3 (aq.) was added to an aqueous KCl solution gradually and the conductivity of the solution was measured. the plot of conductance (L) versus the volume of AgNO3 is - A L L L L volume volume volume volume (P) (Q) (R) (S) (A) (P) (B) (Q) (C) (R) (D) (S) 2. Ans.(D) As AgNO3 is added K+ + Cl– + Ag+ + NO3 ¾® AgCl(s)¯ + K+ + NO3 – – Number of ions are approximately constant, when AgNO3 is added till equivalence point. After equivalence point number of ions, increases and hence conductivity. Corporate Office : ALLEN CAREER INSTITUTE, “SANKALP”, CP-6, INDRA VIHAR, KOTA-324005 PHONE : +91 - 744 - 2436001, Fax : +91-744-2435003, E-mail: info@allen.ac.in Website: www.allen.ac.in 1 / 28 IIT-JEE 2011 EXAMINATION PAPER - 1 (HELD ON : 10 - 04 - 2011) 3. Bombardment of aluminium by a-particle leads to its artificial disintegration in two ways, (i) and (ii) as shown. Products X, Y and Z respectively are : 27 (ii) 30 13 Al 15 P + Y (i) 30 30 14 Si + X 14Si + Z (A) proton, neutron, positron (B) neutron, positron, proton (C) proton, positron, neutron (D) positron, proton, neutron 3. Ans.(A) (i) 27 13 Al + 2 He ¾¾ 14 Si + 1P 4 ® 30 1 (ii) 27 13 ENAl + 2 He ¾¾ 15 P + 1 n 4 ® 30 30 14 0 Si + 1 e X ® proton, Y ® neutron, Z ® positron 0 LL 4. Extra pure N2 can be obtained by heating (A) NH3 with CuO (B) NH4NO3 (C) (NH4)2Cr2O7 (D) Ba(N3)2 4. Ans.(D) A Extra pure N2 can be obtained by heating of Ba(N3)2 D ® Ba(N3)2 ¾¾ Ba+ 3N2 5. Among the following compounds, the most acidic is (A) p-nitrophenol (B) p-hydroxybenzoic acid (C) o-hydroxybenzoic acid (D) p-toluic acid 5. Ans.(C) 1 O O O C H C–OH Intramolecular OH O H-bonding Most acidic Conjugate base Due to ortho effect and chelation in its conjugate base, o-hydroxy benzoic acid is most acidic. Corporate Office : ALLEN CAREER INSTITUTE, “SANKALP”, CP-6, INDRA VIHAR, KOTA-324005 2 / 28 PHONE : +91 - 744 - 2436001, Fax : +91-744-2435003, E-mail: info@allen.ac.in Website: www.allen.ac.in IIT-JEE 2011 EXAMINATION PAPER - 1 (HELD ON : 10 - 04 - 2011) 6. The major product of the following reaction is O C (i) KOH NH C (ii) Br CH2Cl O O O C C (A) N–CH2 Br (B) N CH2Cl C C O O O O C C 6. (C) Ans.(A) EN O C N O–CH2– Br O C (D) N O CH2Cl – + N–H + KOH N K LL C C O O Br CH2 – Cl O A C N – CH2 Br C O 7. Dissolving 120 g of urea (mol. wt. 60) in 1000 g of water gave a solution of density 1.15 g/mL. The molarity of the solution is (A) 1.78 M (B) 2.00 M (C) 2.05 M (D) 2.22 M 7. Ans.(C) Mass of solute (urea) = 120 g Mass of solvent (water) = 1000 g Total mass of solution = (mass of solute + mass of solvent) = 120 + 1000 = 1120 g 2 M= ´ 1000 = 2.05 M 1120 /1.15 Corporate Office : ALLEN CAREER INSTITUTE, “SANKALP”, CP-6, INDRA VIHAR, KOTA-324005 PHONE : +91 - 744 - 2436001, Fax : +91-744-2435003, E-mail: info@allen.ac.in Website: www.allen.ac.in 3 / 28 IIT-JEE 2011 EXAMINATION PAPER - 1 (HELD ON : 10 - 04 - 2011) SECTION - II (TOTAL MARKS : 16) (Multiple Correct Answers Type) This section contains 4 multiple choice questions. Each questions has four choices (A), (B), (C) and (D) out of which ONE or MORE may be correct. 8. Extraction of metal from the ore cassiterite involves (A) carbon reduction of an oxide ore (B) self-reduction of a sulphide ore (C) removal of copper impurity (D) removal of iron impurity 8. Ans.(A,C,D) Extraction of tin from cassiterite (SnO2) involves reduction of ore (oxide) by carbon. When the concentrated tin stone ore SnO2 (ore of Sn) is heated strongly in a free supply of air (roasting) the impurities of CuS and FeS present in the ore are converted into CuSO4 and FeSO4 respectively. The CuSO4 and FeSO4 are water soluble which are leached out by hot water. 9. END ® D CuS + 2O2 ¾¾ CuSO4 ; FeS + 2O2 ¾¾ FeSO4 ® Amongst the given option, the compound(s) in which all the atoms are in one plane in all the possible conformations (if any), is (are) - H H H C–C LL (A) (B) H – C º C – C H2C CH2 CH2 (C) H2C = C = O (D) H2C = C = CH2 9. Ans.(B,C) A H H CH2 (a) Different conformations don’t have all atoms in the same plane. CH2 CH2 (b) H–CºC–C Molecular plane H H (c) C=C=O Molecular plane H H H (d) C=C=C All atoms are not present in the same plane. H H Ans. is (B) and (C) Corporate Office : ALLEN CAREER INSTITUTE, “SANKALP”, CP-6, INDRA VIHAR, KOTA-324005 4 / 28 PHONE : +91 - 744 - 2436001, Fax : +91-744-2435003, E-mail: info@allen.ac.in Website: www.allen.ac.in IIT-JEE 2011 EXAMINATION PAPER - 1 (HELD ON : 10 - 04 - 2011) 10. The correct statement(s) pertaining to the adsorption of a gas on a solid surface is (are) - (A) Adsorption is always exothermic (B) Physisorption may transform into chemisorption at high temperature (C) Physisorption increases with increasing temperature but chemisorption decreases with increasing temperature (D) Chemisorption is more exothermic than physisorption, however it is very slow due to higher energy of activation 10. Ans.(A,B,D) Note : Option (A) is correct as per NCERT book but few examples are known where DHadsorption is even endothermic. 11. According to kinetic theory of gases 11. EN (A) collisions are always elastic (B) heavier molecules transfer more momentum to the wall of the container (C) only a small number of molecules have very high velocity (D) between collisions, the molecules move in straight lines with constant velocities. Ans.(A,B,C,D) LL SECTION - III (TOTAL MARKS : 15) (Paragraph Type) This section contains 2 paragraphs. Based upon one of the paragraph, 3 multiple choice questions and based on the other paragraph 2 multiple choice questions have to be answered. Each of these questions has four choices (A), (B), (C) and (D), out of which ONLY ONE is correct. A Paragraph for Questions Nos. 12 to 14 When a metal rod M is dipped into an aqueous colourless concentrated solution of compound N, the solution turns light blue. Addition of aqueous NaCl to the blue solution gives a white precipitate O. Addition of aqueous NH3 dissolves O and gives in intense blue solution. 12. The metal rod M is - (A) Fe (B) Cu (C) Ni (D) Co 13. The compound N is - (A) AgNO3 (B) Zn(NO3)2 (C) Al(NO3)3 (D) Pb(NO3)2 14. The final solution contains - (A) [Pb(NH3)4]2+ and [CoCl4]2– (B) [Al(NH3)4]3+ and [Cu(NH3)4]2+ (C) [Ag(NH3)2]+ and [Cu(NH3)4]2+ (D) [Ag(NH3)2]+ and [Ni(NH3)6]2+ Corporate Office : ALLEN CAREER INSTITUTE, “SANKALP”, CP-6, INDRA VIHAR, KOTA-324005 PHONE : +91 - 744 - 2436001, Fax : +91-744-2435003, E-mail: info@allen.ac.in Website: www.allen.ac.in 5 / 28 IIT-JEE 2011 EXAMINATION PAPER - 1 (HELD ON : 10 - 04 - 2011) Sol. of 12 to 14 M - Cu , N - AgNO3 , O - AgCl Cu + 2AgNO3 ¾® Cu(NO3)2 + 2Ag + AgNO3 (unreacted) excess light Blue AgNO3 + NaCl ¾® AgCl¯ + NaNO3 (unreacted) white ppt AgCl + 2NH3 ¾® [Ag(NH3)2]+ + Cl– Cu(NO3)2 + 4 NH3 ¾® [Cu(NH3)4]2+ + NO3 – deep Blue 12. Ans.(B) 13. Ans.(A) 14. Ans.(C) EN Paragraph for Questions Nos. 15 to 16 An acyclic hydrocarbon P, having molecular formula C6H10, gave acetone as the only organic product through the following sequence of reactions, in the which Q is an intermediate organic compound. (i) dil H2SO4 /HgSO4 (i) conc.H2SO4 (Catalytic amount) (–H2O) O P Q 2 C LL (C6H10) (ii) NaBH4/ethanol (ii) O3 H3C CH3 (iii) dil.acid (iii) Zn/H2O 15. The structure of compound P is - (A) CH3CH2CH2CH2–CºC–H (B) H3CH2CºC–CH2CH3 A H3C H3C (C) H–C–CºC–CH3 (D) H3C–C–CºC–H H3C H3C 16. The structure of the compound Q is - H3C OH H3C OH (A) H–C–C–CH2CH3 (B) H3C–C–C–CH3 H3C H H3C H H3C OH OH (C) H–C–CH2CHCH3 (D) CH3CH2CH2CHCH2CH3 H3C Corporate Office : ALLEN CAREER INSTITUTE, “SANKALP”, CP-6, INDRA VIHAR, KOTA-324005 6 / 28 PHONE : +91 - 744 - 2436001, Fax : +91-744-2435003, E-mail: info@allen.ac.in Website: www.allen.ac.in IIT-JEE 2011 EXAMINATION PAPER - 1 (HELD ON : 10 - 04 - 2011) Sol. of 15 to 16 15. Ans.(D) 16. Ans.(B) HgSO4/dil.H 2SO 4 P Þ Me3C – C º CH Me3C – C – CH3 O NaBH4 / Ethanol dil.acid H3 C + H3C H3 C + 1,2 shift H2SO4 C – CH – CH3 C – CH – CH 3 – H3C C – CH – CH 3 H3 C of CH3 H3C H3C CH3 CH3 OH + –H O H3 C CH3 O3/Zn C= C 2 C H3 C CH3 EN H3 C CH3 SECTION - IV (TOTAL MARKS : 28) (Integer Answer Type) This section contains 7 questions. The answer to each of the questions is a single-digit integer, ranging from 0 to 9. The bubble corresponding to the correct answer is to be darkened in the ORS. LL 17. Reaction of Br2 with Na2CO3 in aqueous solution gives sodium bromide and sodium bromate with evolution of CO2 gas. The number of sodium bromide molecules involved in the balanced chemical equation is. 17. Ans.(5) OH – disproportionation reaction ® 3Br2 + 3Na2CO3 ¾¾¾¾¾¾¾¾¾ 5NaBr + NaBrO3 + 3CO2 A 18. The difference in the oxidation numbers of the two types of sulphur atoms in Na2S4O6 is. 18. Ans.(5) O O Na O — S — S — S — S — O Na O (+5) (0) O Hence, the difference in oxidation states of ‘S’ atom = 5 – 0 = 5 19. The maximum number of electrons that can have principal quantum number, n=3, and spin quantum number, ms = – 1/2, is 19. Ans.(9) No. of e– having ms=–1/2 n=3, l=0 1 l=1 3 l=2 5 Total No. of e– = 1 +3+5 =9 Corporate Office : ALLEN CAREER INSTITUTE, “SANKALP”, CP-6, INDRA VIHAR, KOTA-324005 PHONE : +91 - 744 - 2436001, Fax : +91-744-2435003, E-mail: info@allen.ac.in Website: www.allen.ac.in 7 / 28 IIT-JEE 2011 EXAMINATION PAPER - 1 (HELD ON : 10 - 04 - 2011) 20. A decapeptide (Mol. Wt. 796) on complete hydrolysis gives glycine (Mol. Wt. 75), alanine and phenylalanine. Glycine contributes 47.0% to the total weight of the hydrolysed products. The number of glycine units present in the decapeptide is 20. Ans.(6) No. of peptide linkage = No. of water molecules added for complete hydrolysis. =n–1 So, number of molecules of H2O added = 9 So total wt. of the product = Mol. wt. of polypeptide + total wt. of H2O added. = 796 + (9 × 16) = 796 + 162 = 958 47 \ wt. of glycine obtained = 958 × ; 450 100 21. EN No. of units of glycine = 450 75 = 6 units To an evacuated vessel with movable piston under external pressure of 1 atm., 0.1 mol of He and 1.0 mol of an unknown compound (vapour pressure 0.68 atm. at 0°C) are introduced. Considering the ideal gas behaviour, the total volume (in litre) of the gases at 0°C is close to LL P =1atm 21. Ans.(7) Since external pressure is 1 atm PV + PHe = 1 Þ PHe = 1 – 0.68 = 0.32 atm Now from idal gas equation Þ PV = nRT 0.1 mol He A PV=0.68 atm Þ 0.32 × V = 0.1 × (R × 273) 1 mol X(s) Þ V = 7 litre. 22. The total number of alkenes possible by dehydrobromination of 3-bromo-3-cyclopentylhexane using alcoholic KOH is 22. Ans.(5) Br C–C–C–C–C–C C–C–C–C–C–C C–C=C–C–C–C C–C–C=C–C–C alcoholic + + KOH 1 product 2 products 2 products (Geometrical isomers) (Geometrical isomers) Corporate Office : ALLEN CAREER INSTITUTE, “SANKALP”, CP-6, INDRA VIHAR, KOTA-324005 8 / 28 PHONE : +91 - 744 - 2436001, Fax : +91-744-2435003, E-mail: info@allen.ac.in Website: www.allen.ac.in IIT-JEE 2011 EXAMINATION PAPER - 1 (HELD ON : 10 - 04 - 2011) 23. The work function (f) of some metals is listed below. The number of metals which will show photoelectric effect when light of 300 nm wavelength falls on the metal is : :- Metal Li Na K Mg Cu Ag Fe Pt W f(eV) 2.4 2.3 2.2 3.7 4.8 4.3 4.7 6.3 4.75 23. Ans.(4) l = 300 nm 1240 E = l in nm eV 1240 = eV 300 = 4.13 eV EN To show photoelectric effect E ³ f. Total no. of metals that show photoelectric effect will be 4. LL A Corporate Office : ALLEN CAREER INSTITUTE, “SANKALP”, CP-6, INDRA VIHAR, KOTA-324005 PHONE : +91 - 744 - 2436001, Fax : +91-744-2435003, E-mail: info@allen.ac.in Website: www.allen.ac.in 9 / 28 IIT-JEE 2011 EXAMINATION PAPER - 1 (HELD ON : 10 - 04 - 2011) PART - II (PHYSICS) SECTION–I : (Total Marks : 21) (Single Correct Answer Type) This section contains 7 multiple choice questions. Each question has four choices (A), (B), (C) and (D), out of which ONLY ONE is correct. 24. 5.6 liter of helium gas at STP is adiabatically compressed to 0.7 liter. Taking the initial temperature to be T1, the work done in the process is 9 3 15 9 (A) RT (B) RT (C) RT (D) RT 8 1 2 1 8 1 2 1 Ans. (A) 5.6 1 No. of moles = n = = 22.4 4 EN TVg–1= constant ÞT1 (5.6)2/3 = T2 (0.7)2/3 Þ T1(8)2/3 = T2 Þ 4T1 = T2 W= - nRDT g -1 =- 1R ( 3T1 ) ´ 3 4´2 9 = - RT1 . Therefore W 8 external 9 = RT1 8 \\\\\\\\\\\\\\ 25. A ball of mass (m) 0.5 kg is attached to the end of a string having length (L) 0.5 m. The ball is rotated on a horizontal circular path about vertical axis. The maximum L LL tension that the string can bear is 324 N. The maximum possible value of angular velocity of ball (in radian/s) is m (A) 9 (B) 18 (C) 27 (D) 36 Ans. (D) Tsinq=mw2r \\\\\\\\\\\\\\ Tsinq=mw Lsinq 2 A q T = mw2L q 1 ( 2)1 324 = w q 2 2 Therefore w = 36 r z 26. Consider an electric field = , where E0 is a constant. The flux through the shaded area (as shown in the figure) due to this field is (a,0,a)) (a,a,a) (A) 2E0a2 (B) 2E0 a 2 E 0 a2 (0,0,0) (0,a,0) y (C) E0a 2 (D) 2 x Ans. (C) uur f = ò E .dS = Ex projected area perpendiuclar to E (x-axis) = E × a2 Corporate Office : ALLEN CAREER INSTITUTE, “SANKALP”, CP-6, INDRA VIHAR, KOTA-324005 10 / 28 PHONE : +91 - 744 - 2436001, Fax : +91-744-2435003, E-mail: info@allen.ac.in Website: www.allen.ac.in IIT-JEE 2011 EXAMINATION PAPER - 1 (HELD ON : 10 - 04 - 2011) 27. A police car with a siren of frequency 8 kHz is moving with uniform velocity 36 km/hr towards a tall building which reflects the sound waves. The speed of sound in air is 320 m/s. The frequency of the siren heard by the car driver is (A) 8.50 kHz (B) 8.25 kHz (C) 7.75 kHz (D) 7.50 kHz Ans. (A) æ v ö æ v + v0 ö æ 320 ö æ 320 + 10 ö f¢=ç ÷ç ÷ f f¢=ç ´ 8 Þ f ¢ » 8.50 kHz è v - vs ø è v ø Þ è 320 - 10 ÷ ç 320 ÷ øè ø 28. A meter bridge is set-up as shown, to determine an unknown resistance ‘X’ using a standard 10 ohm resistor. The galvanometer shows null point when tapping-key is at 52 cm mark. The end-corrections are 1 cm and 2 cm respectively for the ends A and B. The determined value of ‘X’ is X W A B Ans. (B) EN (A) 10.2 ohm (B) 10.6 ohm x = 10 10 (C) 10.8 ohm (D) 11.1 ohm Apply condition of wheatstone bridge, Þ x= ´ 53 Þx = 10.6 W 52 + 1 48 + 2 50 29. A 2 mF capacitor is charged as shown in figure. The percentage of its 1 2 LL s stored energy dissipated after the switch S is turned to position 2 is V 2m F 8m F (A) 0% (B) 20% (C) 75% (D) 80% Ans. (D) A - - -- - - ----- ----- 2m m 2m m 2 æ 2V ö 2V - x x 8V 1 2 ç ÷ Þ Vi = ´ ( 2) V = V ; U = æ 8V ö + è 5 ø = 4V 2 Q1 = CV , Q1 = 2V, = , x= 2 2 2 8 5 2 f ç ÷ è 5ø 2´2 5 4V 2 4V 2 ´ 100 Loss = Þ % loss = 5 = 80% 5 V2 Corporate Office : ALLEN CAREER INSTITUTE, “SANKALP”, CP-6, INDRA VIHAR, KOTA-324005 PHONE : +91 - 744 - 2436001, Fax : +91-744-2435003, E-mail: info@allen.ac.in Website: www.allen.ac.in 11 / 28 IIT-JEE 2011 EXAMINATION PAPER - 1 (HELD ON : 10 - 04 - 2011) 30. The wavelength of the first spectral line in the Balmer series of hydrogen atom is 6561 Å. The wavelength of the second spectral line in the Balmer series of singly-ionized helium atom is (A) 1215 Å (B) 1640Å (C) 2430Å (D) 4687Å Ans. (A) 1 æ 1 1 ö = Rz 2 ç 2 - 2 ÷ l èn m ø 1 2 æ 1 1ö First line of Balmer of Hydrogen : = R (1) ç 2 - 2 ÷ 6561 è2 3 ø 1 æ 1 1ö Second line of Balmer of single ionized He : = R (z2 ) ç 2 - 2 ÷ l è2 4 ø 5 Dividing : l = 6561 ´ = 1215 Å 9´3 EN SECTION–II : (Total Marks : 16) (Multiple Correct Answer Type) This section contains 4 multiple choice questions. Each question has four choices (A), (B), (C) and (D), out of which ONE or MORE may be correct. 31. A spherical metal shell A of radius RA and a solid metal sphere B of radius RB (<RA) are kept far apart and each is given charge ‘+Q’. Now they are connected by a thin metal wire. Then LL s (A) E A = 0 inside (B) QA > QB (C) s = (D) E A surface < EB surface on on Ans. (ABCD) Q QB Q QA A RB RA RB RA = (because of electrostatic condition) So, A option is true. kQA kQB Q A RA Þ vA = vB Þ R = R Þ Q = R Þ RB < RA So, QB < QA, so B is true A B B B s A 4 pRA R A 2 s A RB Þ = Þ s = s B 4pRB RB 2 B RA , So C is true 1 Enear surface = s × . So, D is also true R Corporate Office : ALLEN CAREER INSTITUTE, “SANKALP”, CP-6, INDRA VIHAR, KOTA-324005 12 / 28 PHONE : +91 - 744 - 2436001, Fax : +91-744-2435003, E-mail: info@allen.ac.in Website: www.allen.ac.in IIT-JEE 2011 EXAMINATION PAPER - 1 (HELD ON : 10 - 04 - 2011) 32. A metal rod of length ‘L’ and mass ‘m’ is pivoted at one end. A thin disk of mass ‘M’ and radius ‘R’ (<L) is attached at its center to the free end of the rod. Consider two ways the disc is attached: (case A). The disc is not free to rotate about its center and (case B) the disc is free to rotated about its center. The rod-disc system performs SHM in vertical plane after being released from the same displaced position. Which of the following statement(s) is(are) true? (A) Restoring torque in case A = Restoring torque in case B (B) Restoring torque in case A < Restoring torque in case B (C) Angular frequency for case A> Angular frequency for case B (D) Angular frequency for case A< Angular frequency for case B Ans. (AD) Torque for both the arrangement is same. Since in case B disc is not rotating, there is no speed of the pendulum at equilibrium in case (B). 33. An electron and a proton are moving on straight parallel paths with same velocity. They enter a semi- infinite region of uniform magnetic field perpendicular to the velocity. Which of the following statement(s) is/are true? (A) they will never come out of the magnetic field region (B) they will come out travelling along parallel paths EN (C) they will come out of the same time (D) they will come out at different times Ans. (BD) By diagram B is true. 2 pm T= p qB LL e Tµm mP > m e Tp > Te So, D is also true. 34. A composite block is made of slabs A, B, C, D and E of different thermal conductivities (given in terms A of a constant K) and sizes (given in terms of length, L) as shown in the figure. All slabs are of same width. Heat ‘Q’ flows only from left to right through the blocks. Then in steady state (A) heat flow through A and E slabs are same heat 0 1L 5L 6L (B) heat flow through slab E is maximum 1L A B 3K E (C) temperature difference across slab E is smallest 2K C 4K 6K (D) heat flow through C= heat flow through B + Heat flow through D 3L D 5K Ans. (ABCD) 4L • In steady state : heat in = heat out. So, A is true • Option B is also true because total heat is flowing through E. B 4R/3 DT A C R/2 R/24 • Q= R R/8 E Q = same D 4R/5 RE is minimum. So, DT is minimum So option C is true R/8 R/4 R/24 DT DT DT • QB = ,Q = , QD = , So, QB + QD= QC. 4R / 3 C 4 R / 2 4R / 5 Hence D is also true. Corporate Office : ALLEN CAREER INSTITUTE, “SANKALP”, CP-6, INDRA VIHAR, KOTA-324005 PHONE : +91 - 744 - 2436001, Fax : +91-744-2435003, E-mail: info@allen.ac.in Website: www.allen.ac.in 13 / 28 IIT-JEE 2011 EXAMINATION PAPER - 1 (HELD ON : 10 - 04 - 2011) SECTION–III : (Total Marks : 15) (Paragraph Type) This section contains 2 paragraphs. Based upon one of the paragraph, 3 multiple choice questions and based on the other paragraph 2 multiple choice questions have to be answered. Each of these questions has four choices (A), (B), (C) and (D), out of which ONLY ONE is correct. Paragraph for Questions Nos. 35 to 37 Phase space diagrams are useful tools in analyzing all kinds of dynamical problems. They are especially useful in studying the changes in motion as initial position and momentum are changed. Here we consider some simple dynamical systems in one-dimension. For such systems, phase space is a plane in which position is plotted along horizontal axis and momentum is plotted along vertical axis. The phase space diagram is x(t) vs. p(t) curve in this plane. The arrow on the curve indicates the time flow. For example, the phase space diagram for a particle moving with constant velocity is a straight line as shown in the figure. We use the sign convention in which position or momentum upwards (or to right) is positive and downwards (or to left) is negative. Momentum EN Position 35. The phase space diagram for a ball thrown vertically up from ground is LL Momentum Momentum Momentum Momentum (A) position (B) position (C) position (D) position A Ans. (D) Initial momentum was positive and final momentum negative. So option (D) is correct. 36. The phase space diagram for simple harmonic motion is a circle centered at the origin. In the figure, the two circles represent the same oscillator but for different initial conditions, and E1 and E2 are the total mechanical energies respectively. Then momentum E1 E2 2a a position (A) = (B) E1=2E2 (C) E1=4E2 (D) E1=16E2 Corporate Office : ALLEN CAREER INSTITUTE, “SANKALP”, CP-6, INDRA VIHAR, KOTA-324005 14 / 28 PHONE : +91 - 744 - 2436001, Fax : +91-744-2435003, E-mail: info@allen.ac.in Website: www.allen.ac.in IIT-JEE 2011 EXAMINATION PAPER - 1 (HELD ON : 10 - 04 - 2011) Ans. (C) 2 E2 æ a ö E µ (amplitude) Þ so2 = ç ÷ Þ E1 = 4 E2 E1 è 2 a ø 37. Consider the spring-mass system, with the mass submerged in water, as shown in the figure. The phase space diagram for one cycle of this system is \\\\\\\\\\\ momentum momentum (A) EN momentum position (B) momentum position (C) (D) LL position position Ans. (B) Since at start time position was positive Paragraph for Question Nos. 38 and 39 A A dense collection of equal number of electrons and positive ions is called neutral plasma. Certain solids containing fixed positive ions surrounded by free electrons can be treated as neutral plasma. Let ‘N’ be the number density of free electrons, each of mass ‘m’. When the electrons are subjected to an electric field, they are displaced relatively away from the heavy positive ions. If the electric field becomes zero, the electrons begins to oscillate about the positive ions with a natural angular frequency ‘wr’, which is called the plasma frequency. To sustain the oscillations, a time varying electric field needs to be applied that has an angular frequency w, where a part of the energy is absorbed and a part of it is reflected. As w approaches wr, all the free electrons are set to resonance together and all the energy is reflected. This is the explanation of high reflectivity of metals. Corporate Office : ALLEN CAREER INSTITUTE, “SANKALP”, CP-6, INDRA VIHAR, KOTA-324005 PHONE : +91 - 744 - 2436001, Fax : +91-744-2435003, E-mail: info@allen.ac.in Website: www.allen.ac.in 15 / 28 IIT-JEE 2011 EXAMINATION PAPER - 1 (HELD ON : 10 - 04 - 2011) 38. Taking the electronic charge as ‘e’ and the permittivity as ‘e0’, use dimensional analysis to determine the correct expression for wr. Ne me 0 Ne 2 me 0 (A) (B) (C) (D) me 0 Ne me 0 Ne 2 Ans. (C) æ 1 ö ( 2) é Ne 2 ù ç 3÷ C èL ø 1 ê ú= = = [w] ê m Î0 æ ö T 2 2 ë ú û ( M ) ç C3 T ÷ è LMø 39. EN Estimate the wavelength at which plasma reflection will occur for a metal having the density of electrons -11 N » 4 ´ 10 27 m -3 . Take e 0 » 10 and m » 10 -30 , where these quantities are in proper SI units (A) 800 nm (B) 600 nm (C) 300 nm (D) 200 nm Ans. (B) LL 2 pc Ne 2 m Î0 w = 2 pf = = Þ l = 2 pc l m Î0 Ne2 2 ´ 3.14 ´ 3 ´ 108 (10 -30 )(10 -11 ) 9.42 l= = ´ 10 27 ´ 10 -34 = 6 ´ 10 -7 m = 600 nm 1.6 ´ 10 -19 ( 4 ´ 10 27 ) 1.6 A SECTION–IV : (Total Marks : 28) (Integer Answer Type) This Section contains 7 questions. The answer to each of the question is a single digit integer, ranging from 0 to 9. The bubble corresponding to the correct answer is to be darkened in the ORS. 40. A block is moving on an inclined plane making an angle 45° with the horizontal and the coefficient of friction is m. The force required to just push it up the inclined plane is 3 times the force required to just prevent it from sliding down. If we define N =10m, then N is Ans. (5) Force to just prevent it from sliding = mgsinq – mmgcosq Force to just push up the plane = mgsinq + mmgcosq mgsinq + mmgcosq = 3 (mgsinq – mmgcosq) 1 1 æ 1 m ö 1 +m = 3ç - ÷ Þ m = ÞN = 10 m =5 2 2 è 2 2 ø 2 Corporate Office : ALLEN CAREER INSTITUTE, “SANKALP”, CP-6, INDRA VIHAR, KOTA-324005 16 / 28 PHONE : +91 - 744 - 2436001, Fax : +91-744-2435003, E-mail: info@allen.ac.in Website: www.allen.ac.in IIT-JEE 2011 EXAMINATION PAPER - 1 (HELD ON : 10 - 04 - 2011) stick 41. A boy is pushing a ring of mass 2 kg and radius 0.5 m with a stick as shown in the figure. The stick applies a force of 2N on the ring and rolls it without slipping with an acceleration of 0.3 m/s2. The coefficient of friction between the ground and the ring is large enough that rolling always occurs and the coefficient of friction between the stick and the ring is (P/ 10). The value of P is Ground Ans. (4) N1 = 2 N mN1 N1 – f = ma ...(i) (f–mN1)R = mR2a = ma ...(ii) a From equation (i) and (ii) we get W N1 N1 ( 1–m) = 2ma 2 (1–m) = 2 × 2 × 0.3 f 1 – m = 0.6 Þ m = 0.4 42. EN Four point charges, each of +q, are rigidly fixed at the four corners of a square planar soap film of side ‘a’. The surface tension of the soap film is g. The system of charges and planar film are in equilibrium, 1/ N é q2 ù and a=kê ú , where ‘k’ is a constant. Then N is ëg û Ans. (3) LL b q q Line ab divides the soap film into two equal parts. A q q a FBD of half part gÖ2a Kq 2 é 1ù 1 2 ê 2 + ú where K= a ë 2û 4p Î0 1/ 3 1/ 3 Kq 2 æ 1ö Kq 2 æ 1ö é q2 ù é æ 1ö ù g 2a = 2 ç 2 + ÷ ; a = ç 2+ ÷; a=ê ú 3 g è 2ø êK ç 2 + 2 ÷ ú ÞN=3 a è 2ø ëg û ë è øû 1/ 3 é æ 1ö ù where ê K ç 2 + ÷ ú è =k ë 2ø û Corporate Office : ALLEN CAREER INSTITUTE, “SANKALP”, CP-6, INDRA VIHAR, KOTA-324005 PHONE : +91 - 744 - 2436001, Fax : +91-744-2435003, E-mail: info@allen.ac.in Website: www.allen.ac.in 17 / 28 IIT-JEE 2011 EXAMINATION PAPER - 1 (HELD ON : 10 - 04 - 2011) 43. Four solid spheres each of diameter 5 cm and mass 0.5 kg are placed with their centers at the corners of a square of side 4 cm. The moment of inertia of the system about the diagonal of the square is N × 10–4 kg-m2, then N is Ans. (9) 2 2 2 2 2 æ a ö 2 æ a ö ÷ + 5 mR + m ç 2 I = mR2 + mR2 + mR2 + m ç 5 5 5 è 2ø è 2÷ø 8 é8 5 ù I= mR 2 + ma 2 = ê ´ 0.5 ´ + 0.5 ´ 4 2 ú ´ 10 -4 = (1+8) × 10–4 = N × 10–4 ÞN =9 5 ë5 4 û 44. The activity of a freshly prepared radioactive sample is 1010 disintegrations per second, whose mean life is 109 s. The mass of an atom of this radioisotope is 10–25 kg. The mass (in mg) of the radioactive sample is Ans. (1) 1010 A = lN Þ 10 = lN Þ N = 10 = (1010 ) t = 1010 ´ 10 9 = 1019 EN l M = Nm = (1019) (10–25) = 10–6 kg = 1 mg 45. A long circular tube of length 10 m and radius 0.3 m carries a current I along its curved surface as shown. A wire-loop of resistance 0.005 ohm and of radius 0.1 m is placed inside the tube with its axis coinciding with the axis of the tube. The current varies as I=I0cos (300t) where I0 is constant. If the magnetic moment LL of the loop is N m 0 I 0 sin ( 300t ) , then ‘N’ is Ans. (6) æ m0 I ö 2 pr 2 d f æ m 0 I 0 pr 2 ö f = Bpr = ç pr = m 0 I 0 cos300t Þ e1 = =ç ÷ 300 sin 300t è L ÷ 2 ø L dt è L ø A e é pr 2 (300 ) ù é p 2r 4 ( 300 ) ù i= = ( m 0 I 0 sin 300t ) ê Þ M = i pr 2 = ê ú m 0 I 0 sin 300t R ë LR ú û ë LR û 46. Steel wire of length ‘L’ at 40°C is suspended from the ceiling and then a mass ‘m’ is hung from its free end. The wire is cooled down from 40° to 30° C to regain its original length ‘L’. The coefficient of linear thermal expansion of the steel is 10–5/°C, Young’s modulus of steel is 1011 N/m2 and radius of the wire is 1 mm. Assume that L>> diameter of the wire. Then the value of ‘m’ in kg is nearly Ans. (3) Dx YA YA = = aDq Þ m = L mg gaDq (1011 ) ( 3.14) (10 -6 ) m= Þ m = 3.14kg Þ m = 3 (10 ) (10 -5 ) (10 ) Corporate Office : ALLEN CAREER INSTITUTE, “SANKALP”, CP-6, INDRA VIHAR, KOTA-324005 18 / 28 PHONE : +91 - 744 - 2436001, Fax : +91-744-2435003, E-mail: info@allen.ac.in Website: www.allen.ac.in IIT-JEE 2011 EXAMINATION PAPER - 1 (HELD ON : 10-04-2011) PART - III (MATHEMATICS) SECTION–I : (Total Marks : 21) (Single Correct Answer Type) This section contains 7 multiple choice questions. Each question has four choices (A), (B), (C) and (D), out of which ONLY ONE is correct. ln 3 x sin x 2 47. The value of ò sin x 2 + sin(ln 6 - x 2 ) dx is ln 2 1 3 1 3 3 1 3 (A) ln (B) ln (C) ln (D) ln 4 2 2 2 2 6 2 47. Ans.(A) I= ò Þ ln2 ln3 1 EN sin x 2 + sin(ln6 - x 2 ) ; put x = t Þ 2xdx = dt I= ò ln3 x sin x 2 sin t dx 2 ln 2 sin t + sin(ln6 - t) ln3 dt 2 ....(i) 1 sin(ln6 - t) Þ I= ò LL dt ....(ii) 2 ln 2 sin(ln6 - t) + sin t Adding equation (i) & (ii) ln3 1 1 æ3ö Þ 2I = ò dt Þ I = ln ç ÷ 2 ln2 4 è2ø Let the straight line x = b divide the area enclosed by y = (1 – x)2, y = 0 and x = 0 into two parts A 48. 1 R1 (0 £ x £ b) d and R 2 (b £ x £ 1) such that R1 - R 2 = . Then b equals 4 3 1 1 1 (A) (B) (C) (D) 4 2 3 4 y 48. Ans.(B) 1 Q R1 –R2 = 4 b 1 R1 R R2 1 ò (1 - x) dx - ò (1 - x) dx = x 2 2 2 Þ 0 x=b (1,0) 0 b 4 b 1 æ (1 - x)3 ö æ (1 - x) 3 ö 1 ì (1 - b)3 1 ü (1 - b)3 1 Þ -ç ÷ +ç ÷ = Þ -í - ý- = è 3 ø0 è 3 ø b 4 î 3 3þ 3 4 1 2 1 2 1 Þ - (1 - b)3 = Þ (1 - b)3 = 3 3 4 3 12 1 1 1 Þ (1 – b)3 = Þ 1–b= Þ b= 8 2 2 Corporate Office : ALLEN CAREER INSTITUTE, “SANKALP”, CP-6, INDRA VIHAR, KOTA-324005 PHONE : +91 - 744 - 2436001, Fax : +91-744-2435003, E-mail: info@allen.ac.in Website: www.allen.ac.in 19 / 28 IIT-JEE 2011 EXAMINATION PAPER - 1 (HELD ON : 10-04-2011) r r r r Let a = ˆ + ˆ + k, b = ˆ - ˆ + k and r = ˆ - ˆ - k be three vectors. A vector v in the plane of a and b , r 49. i j ˆ i j ˆ c i j ˆ r 1 whose projection on c is , is given by 3 (A) ˆ - 3ˆ + 3k i j ˆ ˆ (B) -3i - 3ˆ - k j ˆ (C) 3i - ˆ + 3k ˆ j ˆ (D) ˆ + 3ˆ - 3k i j ˆ 49. Ans.(C) r r r v = xa + yb = ˆ + y) + ˆ - y) + k(x + y) ....(i) i(x j(x ˆ r 1 Given , v.c = ˆ 3 x+y-x+y-x-y 1 Þ = 50. y–x=1 EN Þ x – y = –1 3 ....(ii) r 3 ˆ j using (ii) in (i) we get v = (x + y)i - ˆ + (x + y)k ˆ Let (x0, y0) be the solution of the following equations ( 2x ) ln 2 = (3y)ln 3 LL 3lnx = 2lny Then x0 is 1 1 1 (A) (B) (C) (D) 6 6 3 2 50. Ans.(C) ln2 ( 2x ) A = (3y) l n 3 Þ ln2 (ln2 + lnx) = ln3(ln3 + lny) .....(i) 3lnx = 2lny Þ (lnx) (ln3) = (lny) (ln2) .....(ii) using (ii) in (i) æ (lnx)(ln3) ö Þ ln2(ln2+lnx)= ln3 ç ln3 + ÷ è ln2 ø ì ln 2 3 ü Þ ln 2 2 - ln 2 3 = lnx í - ln2 ý î ln2 þ Þ lnx = – ln2 1 Þ x= 2 51. Let a and b be the roots of x2 – 6x – 2 = 0, with a > b. If an = an – bn for n ³ 1, then the value a10 - 2a 8 of 2a 9 is (A) 1 (B) 2 (C) 3 (D) 4 Corporate Office : ALLEN CAREER INSTITUTE, “SANKALP”, CP-6, INDRA VIHAR, KOTA-324005 20 / 28 PHONE : +91 - 744 - 2436001, Fax : +91-744-2435003, E-mail: info@allen.ac.in Website: www.allen.ac.in IIT-JEE 2011 EXAMINATION PAPER - 1 (HELD ON : 10-04-2011) 51. Ans. (C) a,b are roots of x2 – 6x – 2 = 0 Þ a2 – 6a –2 = 0 & b2 – 6b – 2 = 0 a 0 - 2a 8 a10 - b10 - 2(a8 - b8 ) = 2a 9 2(a 9 - b9 ) a8 (a2 - 2) - b8 (b2 - 2) = 2(a9 - b9 ) a8 .6a - b8 .6b = =3 2(a9 - b9 ) 52. A straight line L through the point (3, –2) is inclined at an angle 60° to the line 3x + y = 1 . If L 52. also intersect the x-axis, then the equation of L is (A) y + 3x + 2 - 3 3 = 0 (C) Ans. (B) EN 3y - x + 3 + 2 3 = 0 (B) y - 3x + 2 + 3 3 = 0 (D) 3y + x - 3 + 2 3 = 0 (0,1) p LL Line L has two possible slopes with inclination; q = , q = 0 3 p 2p/3 \ equation of line L when q = , y+2= 3(x - 3) 3 GH 1 3 ,0 JK 3x+y=1 Þ y - 3x + 2 + 3 3 = 0 A equation of line L when q = 0, y = –2 (rejected) \ required line L is y - 3x + 2 + 3 3 = 0 53. { } { Let P = q : sin q - cos q = 2 cos q and Q = q : sin q + cos q = 2 sin q be two sets. Then } (A) P Ì Q and Q - P ¹ Æ (B) Q Ì P / (C) P Ì Q / (D) P = Q 53. Ans.(D) P = {q : sinq – cosq = 2 cosq} Þ tanq = 2 +1 ...(i) Q = {q : sinq + cos q = 2 sinq} 1 Þ tan q = = 2 +1 ...(ii) 2 -1 from (i) & (ii) Þ P=Q Corporate Office : ALLEN CAREER INSTITUTE, “SANKALP”, CP-6, INDRA VIHAR, KOTA-324005 PHONE : +91 - 744 - 2436001, Fax : +91-744-2435003, E-mail: info@allen.ac.in Website: www.allen.ac.in 21 / 28 IIT-JEE 2011 EXAMINATION PAPER - 1 (HELD ON : 10-04-2011) SECTION–II : (Total Marks : 16) (Multiple Correct Answer Type) This section contains 4 multiple choice questions. Each question has four choices (A), (B), (C) and (D), out of which ONE or MORE may be correct. 54. ˆ j ˆ The vector(s) which is/are coplanar with vectors ˆ + ˆ + 2k and ˆ + 2ˆ + k , and perpendicular to the i j i i j ˆ vector ˆ + ˆ + k is/are j ˆ (A) ˆ - k (B) -ˆ + ˆ i j (C) ˆ - ˆ i j ˆ (D) -ˆj + k Sol. Ans. (A,D) r r r a = ˆ + ˆ + 2k i j ˆ b = ˆ + 2ˆ + k i j ˆ i j ˆ c = ˆ+ˆ+k r r r r rr r rr r v = l((a ´ b) ´ c) = l((a.c)b - (b.c)a r 55. r EN v = l[4(i + 2 ˆ + k) - 4(i + ˆ + 2k)] ˆ v = 4 l(ˆ - k) j ˆ j ˆ ˆ j ˆ Let ƒ : R ® R be a function such that ƒ(x + y) = ƒ(x) + ƒ(y), " x, y Î R. If ƒ(x) is differentiable at x = 0, then (A) ƒ(x) is differentiable only in a finite interval containing zero LL (B) ƒ(x) is continuous " x Î R (C) ƒ'(x) is constant " x Î R (D) ƒ(x) is differentiable except at finitely many points Sol. Ans. (B,C) ƒ(x + y) = ƒ(x) + ƒ(y) A ƒ(0) = 0 ƒ(x + h) - ƒ(x) ƒ(x) + ƒ(h) - ƒ(x) ƒ'(x) = lim = lim h ®0 h h ®0 h ƒ(h) ƒ(0 + h) - ƒ(0) = lim = lim h ®0 h h ®0 h ƒ'(x) = ƒ'(0) = k (k is constant) Þ ƒ(x) = kx, hence ƒ(x) is continuous and ƒ'(x) is constant " x Î R 56. Let M and N be two 3 × 3 non-singular skew-symmetric matrices such that MN = NM. If PT denotes the transpose of P, then M2N2(MTN)–1 (MN–1)T is equal to - (A) M2 (B) –N2 (C) –M2 (D) MN Sol. Ans. (C) (Comment : Although 3 × 3 skew symmetric matrices can never be non-singular. Therefore the information given in question is wrong. Now if we consider only non singular skew symmetric matrices M & N, then the solution is-) Given MT = –M NT = –N MN = NM Corporate Office : ALLEN CAREER INSTITUTE, “SANKALP”, CP-6, INDRA VIHAR, KOTA-324005 22 / 28 PHONE : +91 - 744 - 2436001, Fax : +91-744-2435003, E-mail: info@allen.ac.in Website: www.allen.ac.in IIT-JEE 2011 EXAMINATION PAPER - 1 (HELD ON : 10-04-2011) according to question M2N2(MTN)–1 (MN–1)T = M2N2N–1(MT)–1(N–1)TMT é MN = NM 2 2 –1 = M N N (–M) (N ) (–M)–1 T –1 ê -1 -1 ê (MN) = (NM) = –M2 N M–1 N–1 M ê N -1M -1 = M -1N -1 ë = – M2 N N–1 M–1 M = –M2 x 2 y2 57. Let the eccentricity of the hyperbola 2 - 2 = 1 be reciprocal to that of the ellipse x2 + 4y2 = 4. a b If the hyperbola passes through a focus of the ellipse, then - x2 y 2 (A) the equation of the hyperbola is - =1 3 2 (B) a focus of the hyperbola is (2,0) EN (C) the eccentricity of the hyperbola is 2 5 3 (D) the equation of the hyperbola is x – 3y2 = 3 Sol. Ans. (B,D) x 2 y2 Given hyperbola is 2 - 2 = 1 LL a b x 2 y2 ellipse is + =1 22 1 1 3 3 eccentricity of ellipse = 1- = = 4 4 2 A b2 4 eccentricity of hyperbola = 1+ = a2 3 b2 1 Þ = Þ 3b2 = a2 ...........(1) a2 3 also hyperbola passes through foci of ellipse ( ± 3, 0) 3 =1 Þ a2 = 3 ............(2) a2 from (1) & (2) b2 = 1 x 2 y2 equation of hyperbola is - =1 Þ x2 – 3y2 = 3 3 1 1 4 eccentricity of hyperbola = 1 + = 3 3 æ 2 ö focus of hyperbola = ç ± 3. , 0 ÷ º ( ±2, 0 ) è 3 ø Corporate Office : ALLEN CAREER INSTITUTE, “SANKALP”, CP-6, INDRA VIHAR, KOTA-324005 PHONE : +91 - 744 - 2436001, Fax : +91-744-2435003, E-mail: info@allen.ac.in Website: www.allen.ac.in 23 / 28 IIT-JEE 2011 EXAMINATION PAPER - 1 (HELD ON : 10-04-2011) SECTION–III : (Total Marks : 15) (Paragraph Type) This section contains 2 paragraphs. Based upon one of the paragraph, 3 multiple choice questions and based on the other paragraph 2 multiple choice questions have to be answered. Each of these questions has four choices (A), (B), (C) and (D), out of which ONLY ONE is correct. Paragraph for Question 58 and 60 Let a,b and c be three real numbers satisfying é1 9 7ù [ a b c ] ê8 2 7 ú = [ 0 0 0 ] ê ú ...(E) ê 7 3 7ú ë û 58. If the point P(a,b,c), with reference to (E), lies on the plane 2x + y + z = 1, then the value of 7a+b+c is 59. 60. (A) 0 value of (A) –2 EN Let w be a solution of x – 1 = 0 with Im(w) > 0. If a = 2 with b and c satisfying (E), then the 3 + b + c is equal to - w w w a 1 3 (B) 12 (B) 2 3 (C) 3 (C) 7 (D) –3 (D) 6 Let b = 6, with a and c satisfying (E). If a and b are the roots of the quadratic equation LL n æ1 1ö ¥ ax + bx + c = 0, then å ç + ÷ is- 2 n= 0 è a bø 6 (A) 6 (B) 7 (C) (D) ¥ 7 Sol. Paragraph for Question 58 to 60 A a + 8b + 7c = 0 9a + 2b + 3c = 0 7a + 7b + 7c = 0 Þ a = K, b = 6K , c = –7K 58. Ans. (D) (K, 6K, –7K) 2x + y + z = 1 2K + 6K – 7K = 1 (Q point lies on the plane) Þ K=1 Þ 7a + b + c = 7K + 6K – 7K = 6 59. Ans. (A) x3 – 1 = 0 Þ x = 1, w, w2 1 i 3 w= - + since Im(w) > 0 2 2 If a = 2 = K Þ b = 12 & c = –14 Corporate Office : ALLEN CAREER INSTITUTE, “SANKALP”, CP-6, INDRA VIHAR, KOTA-324005 24 / 28 PHONE : +91 - 744 - 2436001, Fax : +91-744-2435003, E-mail: info@allen.ac.in Website: www.allen.ac.in IIT-JEE 2011 EXAMINATION PAPER - 1 (HELD ON : 10-04-2011) 3 1 3 3 1 3 Hence + b + c = 2 + 12 + -14 = 3w+1+3w2 w w w w w a w = –3 + 1 = –2 60. Ans. (B) Q b = 6 Þ 6K = 6 Þ K = 1 Þ a = 1, b = 6 & c = –7 2 x + 6x – 7 = 0 Þ a + b = –6 , ab = –7 n n æ a +b ö ¥ ¥ æ6ö 1 å ç ab ÷ = å ç 7 ÷ = 6 = 7 Þ n =0 è n =0 è ø 1- ø 7 Sol. Paragraph for Question 61 and 62 (A) 13 EN Let U1 and U2 be two urns such that U1 contains 3 white and 2 red balls, and U2 contains only 1 white ball. A fair coin is tossed. If head appears then 1 ball is drawn at random from U1 and put into U2. However, if tail appears then 2 balls are drawn at random from U1 and put into U2. Now 1 ball is drawn at random from U2. 61. The probability of the drawn ball from U2 being white is - (B) 23 (C) 19 (D) 11 30 30 30 30 LL 62. Given that the drawn ball from U2 is white, the probability that head appeared on the coin is - 17 11 15 12 (A) (B) (C) (D) 23 23 23 23 Paragraph for Question 61 and 62 U1 U2 A 3W 2R 1 ball 1W 1/2 d a He Start 1 U1 U2 Ta /2 il 3W 1W 2R 2 balls 61. Ans. (B) Required probability 2 1 ö 1 æ 3C C 1 3C C 2 ö 2 2 1æ 3 = ç .1 + . ÷ + ç 5 2 .1 + 5 2 . + 5 1 1 . ÷ 2è 5 5 2 ø 2 è C2 C2 3 C2 3 ø 1 æ 4 ö 1 æ 3 1 2 ö 2 11 23 = ç ÷+ ç + + ÷ = + = 2 è 5 ø 2 è 10 30 5 ø 5 30 30 62. Ans. (D) Required probability 2/5 = (using Baye's theorem) 2 / 5 + 11/ 30 12 = 23 Corporate Office : ALLEN CAREER INSTITUTE, “SANKALP”, CP-6, INDRA VIHAR, KOTA-324005 PHONE : +91 - 744 - 2436001, Fax : +91-744-2435003, E-mail: info@allen.ac.in Website: www.allen.ac.in 25 / 28 IIT-JEE 2011 EXAMINATION PAPER - 1 (HELD ON : 10-04-2011) SECTION–IV : (Total Marks : 28) (Integer Answer Type) This Section contains 7 questions. The answer to each of the question is a single digit integer, ranging from 0 to 9. The bubble corresponding to the correct answer is to be darkened in the ORS. p 63. Let a1,a2,a3,.........,a100 be an arithmetic progression with a1 = 3 and Sp = å a i ,1 £ p £ 100 . For any i =1 Sm integer n with 1 < n < 20, let m = 5n. If S does not depend on n, then a2 is n Sol. Ans. 9 or 3 (Comment : The information about the common difference i.e. zero or non-zero is not given in the question. Hence there are two possible answers) a1 = 3 ; m = 5n EN Consider d ¹ 0 the solution is a1, a2, a3, ............, a100 ® AP p Sp = å a i i =1 1 £ n £ 20 m LL [2a1 + (m - 1)d] Sm = 2 Sn n [2a1 + (n - 1)d] 2 Sm 5[(2a 1 - d) + 5nd] = Sn [(2a1 - d) + nd] A Sm for to be independent of n Sn \ 2a1 – d = 0 Þ d = 2a1 Þ d = 6 Þ a2 = 9 If d = 0 Þ a2 = a1 = 3 64. Consider the parabola y2 = 8x. Let D1 be the area of the triangle formed by the end points of its æ1 ö latus rectum and the point P ç , 2 ÷ on the parabola, and D2 be the area of the triangle formed by è2 ø D1 drawing tangents at P and at the end points of the latus rectum. Then D is 2 Sol. Ans. 2 (2,4) A D1 = area of D PAA' (1/2,2) y = 8x 2 P Þa=2 1 3 = .8. = 6 2 2 1 D2 = (D1) 2 A' (2,–4) (Using property : Area of triangle formed by tangents is always half of original triangle) Corporate Office : ALLEN CAREER INSTITUTE, “SANKALP”, CP-6, INDRA VIHAR, KOTA-324005 26 / 28 PHONE : +91 - 744 - 2436001, Fax : +91-744-2435003, E-mail: info@allen.ac.in Website: www.allen.ac.in IIT-JEE 2011 EXAMINATION PAPER - 1 (HELD ON : 10-04-2011) D1 Þ =2 D2 65. The positive integer value of n > 3 satisfying the equation 1 1 1 = + is æpö æ 2p ö æ 3p ö sin ç ÷ sin ç ÷ sin ç ÷ ènø è n ø è n ø Sol. Ans. 7 1 1 1 1 1 1 = + Þ - = p 2p 3p p 3p 2p sin sin sin sin sin sin n n n n n n 3p p 2p p - sin sin 2cos sin n n = 1 n n = 1 Þ Þ Þ 2cos Þ sin p sin sin n EN 3p n 4p 2p n sin sin = sin n 2p n 2p 3p sin sin = sin Þ 4p p n 3p n 3p n sin = Kp + ( -1) K 3p 2p n n n n n LL p 1 1 1 1 If K = 2m Þ = 2mp Þ n= Þ n= , , ........ n 2m 2 4 6 7p 7 7 7 If K = 2m + 1 = (2m + 1) p Þ Þ n= Þ n = 7, , ....... n 2m + 1 3 5 A Possible value of n is 7 æ -1 æ sin q ö ö p p d 66. Let ƒ(q) = sin ç tan ç ÷ ÷ , where - 4 < q < 4 . Then the value of (ƒ(q)) is è è cos2q ø ø d(tan q) Sol. Ans. 1 -1 æ sin q ö Let ƒ( q) = sin a where a = tan ç ÷ è cos 2q ø sin q Þ tan a = cos 2q sin q æ æ p p öö Þ sin a = = tan q çQ q Î ç - , ÷ ÷ cos q è è 4 4 øø Þ ƒ( q) = tan q d(ƒ(q)) Þ =1 d(tan q) 67. If z is any complex number satisfying |z – 3 – 2i| < 2, then the minimum value of |2z – 6 + 5i| is Corporate Office : ALLEN CAREER INSTITUTE, “SANKALP”, CP-6, INDRA VIHAR, KOTA-324005 PHONE : +91 - 744 - 2436001, Fax : +91-744-2435003, E-mail: info@allen.ac.in Website: www.allen.ac.in 27 / 28 IIT-JEE 2011 EXAMINATION PAPER - 1 (HELD ON : 10-04-2011) Sol. Ans. 5 Im æ 5 ö We have to find minimum value of 2 z - ç 3 - i ÷ è 2 ø |z–3–2i| < 2 æ 5ö (3,2) = 2 × (minimum distance between z and point ç 3, - ÷ ) è 2ø = 2 × (distance between (3,0) and æ 3, - ö ) 5 Re (3,0) ç ÷ è 2ø (3,–5/2) 5 =2× = 5 units. 2 68. The minimum value of the sum of real numbers a–5, a–4, 3a–3, 1, a8 and a10 with a > 0 is Sol. Ans. 8 As a > 0 and all the given terms are positive Þ EN hence considering A.M. > G.M. for given numbers : a -5 + a -4 + a -3 + a -3 + a -3 + a 8 + a10 7 ³ ( a .a .a .a .a .a .a ) a -5 + a -4 + a -3 + a -3 + a -3 + a 8 + a10 7 -5 -4 -3 -3 -3 8 10 7 ³1 Þ 1 (a -5 + a -4 + 3a -3 + a 8 + a10 ) min =7 where a–5 = a–4 = a–3 = a8 = a10 i.e. a = 1 LL Þ (a–5 + a–4 + 3a–3 + a8 + a10 + 1)min = 8 when a = 1 x 69. Let ƒ : [1,¥) ® [2,¥) be a differentiable function such that f(1) = 2. If 6 ò ƒ(t)dt = 3x ƒ(x) - x 3 1 for all x > 1, then the value of ƒ(2) is A Sol. Ans. 6 (Comment : The given relation does not hold for x =1, therefore it is not an identity. Hence there is an error in given question. The correct identity must be-) x 6 ò f(t)dt = 3xf(x) – x 3 – 5, " x ³ 1 1 Now applying Newton Leibnitz theorem 6ƒ(x) = 3xƒ'(x) – 3x2 + 3ƒ(x) Þ 3ƒ(x) = 3xƒ'(x) – 3x2 Let y = ƒ(x) dy xdy - ydx æ yö Þ x dx - y = x2 Þ x2 = dx Þ ò d ç x ÷ = ò dx è ø y Þ = x+C (where C is constant) x Þ y = x2 + Cx \ ƒ(x) = x2 + Cx Given ƒ(1) = 2 Þ C = 1 \ ƒ(2) = 22 + 2 = 6 Corporate Office : ALLEN CAREER INSTITUTE, “SANKALP”, CP-6, INDRA VIHAR, KOTA-324005 28 / 28 PHONE : +91 - 744 - 2436001, Fax : +91-744-2435003, E-mail: info@allen.ac.in Website: www.allen.ac.in

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PREVIOUS YEAR PAPERS CBSE BOARD EXAM AIEEE BITSAT ISAT VITEEE IIT-JEE STUDY MATERIAL PHYSICS CLASS XI XII SAMPLE PAPERS KEY SOLUTIONS ANSWERS QUESTIONS

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